Novel developer and process

ABSTRACT

A photographic developer for high contrast, thin emulsion films comprising an aqueous alkaline solution of a 3-pyrazolidone as a primary developing agent and secondary developing agent which synergistically combines with the 3-pyrazolidone to yield a super-additive developer combination. A process which produces continuous print tones with a high contrast negative emulsion. A concentrated solution of the developer and a process for forming the same.

United States Patent [191 Holden et al.

[ Nov. 13, 1973 NOVEL DEVELOPER AND PROCESS [75] Inventors: Harold Holden; Arnold Weichert,

both of St. .lohnsbury, Vt.

[73] Assignee: The H & W Company Inc., St.

Johnsbury, Vt.

[22] Filed: May 19, 1972 [21] Appl. No.: 255,000

Related U.S. Application Data [63] Continuation-impart of Ser. No. 846,215, July 30, 1969, abandoned, and a continuation-in-part of Ser. No. 28,537, April 14, 1970, abandoned, said Ser. No. 28,537, is a continuation-in-part of Ser. No. 846,215.

3,632,341 l/l972 Zacchia 96/66 HD 3,716,363 2/1973 Ruggerio 96/66 R FOREIGN PATENTS OR APPLICATIONS 871,684 0/0000 Great Britain 96/66 OTHER PUBLICATIONS Phenidone, Axford & Kendall; pp. 169-172, 1954.

Primary Examiner-Norman G. Torchin Assistant ExaminerM. F. Kelley Att0rneyRichard C. Sughrue et al.

[57] ABSTRACT v A photographic developer for high contrast, thin emulsion films comprising an aqueous alkaline solution of a 3-pyrazolidone as a primary developing agent and secondary developing agent which synergistically combines with the 3-pyrazolidone to yield a superadditive developer combination.

A process which produces continuous print tones with a high contrast negative emulsion.

A concentrated solution of the developer and a process for forming the same.

12 Claims, No Drawings NOVEL DEVELOPER AND PROCESS CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of US. application Ser. No. 846,2l5, filed July 30, l969, and U.S. application Ser. No. 28,537, filed Apr. 14, 1970, which is a continuation-in-part of U.S. application Ser. No. 846,215, both entitled Novel Developer and Process" both are now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to thin emulsion photographic developing solutions for high contrast films, a developing process for high contrast thin emulsion films which enables one to obtain continuous print tones, a concentrated developer solution containing a 3-pyrazolidone from which the developer solution for high contrast films is formed, and to a process for forming the concentrated developer solution.

The term developing solution in the present application means a developing solution for high contrast thin emulsion light sensitive silver halide films, unless otherwise indicated.

2. Description of the Prior Art Some typical high contrast copy films are Kodak High Contrast Copy Film and Fuji Microfilm Negative HR. Other high contrast films with extremely high resolution are exemplified by Kodak High Resolution Plates and Kodak Spectroscopic Film, Type 649. In combination with the very thin emulsion which these films exhibit, they also have very fine grain. In the field of this invention, it has been found that such films are useful for continuous-tone photographic purposes, yielding negatives of detail and information content superior to continuous-tone processes previously employed.

However, until the present invention, it has been impossible to process such high contrast copy films to produce a continuous-tone negative when such films were exposed at Exposure Indexes that would enable snap-shooting in ordinary daylight conditions. This is because there has not been a developer formula which would enable the use of these emulsions at a practical Exposure Index.

Applying the knowledge of the prior art in developing high contrast films, the typical result was an end print which illustrated stark black and white outlines; that is, it was impossible to obtain a correctly proportioned gray scale. The present invention overcomes this limitation of the prior art.

Further, high contrast film properly developed can be enlarged a great number of times before the quality of the image is degraded or rendered useless by the characteristics of the emulsion.

There are many developers which produce continuous tones with thicker and coarser-grained emulsions. The inherent flatness or ability to produce a long tonal scale increases with the thickness of the emulsion and the coarseness of the grain. However, in the very thin emulsion, high contrast films, where light strikes there is a tendency to complete exposure, which results in the stark black-and-white image satisfactory for high D76 is a developer of this type. However, the developer must be greatly diluted beyond proportions which are sanctioned by the manufacturer and which would be normal for use with conventional thicker-emulsion films. This has a very serious effect in practice, as this greater dilution necessitates an increase of as much as 16 times in the amount of light which must strike the emulsion to create enough of a latent image to respond to the greatly diluted developer (16 times, or five stops, as much light as required by the developer of the present invention). Perhaps a more serious fault with such developers is that at great dilution they yield an uneven development of the film. The disastrous defect can be traced to a lack of sufficient concentration of the developer.

Accordingly, to use developers such as D-76 they must be greatly diluted, and this results in uneven development and a great decrease in the effective speed of the film.

The 3-pyrazolidones are known to be developing agents. Among the 3-pyrazolidones useful in the present invention are those listed in U.S. Pat. Nos. 2,685,516; 2,688,548; 2,688,549; 2,751,297; 3,021,212; 3,284,200 and 3,241,967. Representative of such compounds are:

1-phenyl-, 1-p-tolyl-, chlorophenyl-,

5-phenyl-, 5-methyl-, 1-p- 1-phenyl-5-phenyl-, 1-m-tolyl-, l-phenyl-S -methyl-, 1 -p-tolyl-5 -phenyl-, 1-pmethoxyphenyl-, 1-acetamidophenyl-, 1 -phenyl-2- acetyl-4,4-dimethyl-, l-phenyl-4,4-dimethyl-, 1-maminophenyl-4-methyl-4-propyl-, l-o-chlorophenyl-4- methyl-4-ethyl-, 1-m-acetamidophenyl-4,4-diethyl-, l- (p-B-hydroxyethylphenyl)-4,4-dimethyl-, 1-phydroxyphenyl-4,4-dimethyl-, l-p-methoxyphenyl-4,4- diethyl-, 1p-tolyl-4,4-dimethyl-, 1-(7-hydroxy-2- naphthyl)-4-methyl-4-n-propyl-, l-p-diphenyl-4,4- dimethyl-, l-(p-B-hydroxyethylphenyl l-o-tolyl, 1-o-tolyl-4,4-dimethyl-, 1-benzothiazolyl-, 1-mnitrophenyl-, l-p-nitrophenyl- 1-p-cyanophenyl-, 1 -p- B-methane-sulfonamidoethylphenyl-, l-( p-carboxymethylphenyl l-(2-benzothiazolyl)-, l-p-aminophenyl- 4-methyl-4-propyl, 1-p-chlorophenyl-4-methyl-4-ethyl- 1-p-acetamidophenyl-4,4-diethyl-, 1 -p-nitrophenyl4,4-dimethyl-, 1-p-cyanophenyl-4,4-dimethyl-, 1-p-benzylphenyl-4,4-dimethyl-, l-carboxymethyl-4,4- dimethyl-, 1-hydroxyethyl-4,4-dimethyl-, l -maminophenyl-4,4-dimethyl-, 1-m-chlorophenyl-4-methyl-4-ethyl-, l-phenyl-4,5 -tetramethylene-, l-phenyl- 4,5 -trimethylene-, 1-m-chlorophenyl-4,5 tetramethylene-, 2-morpholinomethyll -phenyl-, 2- 1,2,3 ,4-tetrahydroquinolylmethyl)-1-phenyl-,

2-piperidinomethyl-1-phenyl-, phenyl-, Z-hydroxymethyl-4-methyl-1-phenyl-, 4 ,4- dimethyl-Z-hydroxymethyll -phenyl-, 4-chloromethyl- 2-hydroxymethyl-4-methyll -phenyl-, Z-(methyI-B- hydroxyethyl )-aminoethyl-4 ,4-dimethyll -phenyl-, 2- (di-B-hydroxyethyl)-aminoethyl-4,4-dimethyl-1- phenyl-, 1-methyl-4,4-dimethyl-, and lp-.

carboxyphenyl-4,4-dimethyl-3-pyrazolidone.

Other useful 3-pyrazolidones are mentioned in Mees and James, The Theory of the Photographic Process, 3rd Edition, Macmillan and Co., New York, 1966, p. 300:

l-phenyl-4ethyl-, l-phenyl-4-isopropyl-, l-phenyl- 5,5-dimethyl, and 1--phenyl-4,S-dimethyl-B- pyrazolidone. 1-phenyl-4-methyl-3-pyrazolidone is also useful.

2-hyroxymethyll I Phenidone derivatives which are somewhat different than those given thus far may be found in Ficken and Sanderson, J. Phot. Sci, 1 l", 157 (1963). A representative sample of these classes is:

l-(4-pyridyl)-, l-(2-pyridyl)-, 1-(6-methyl-2- pyridyl)-, l-(4,6-dirnethyl-2-pyrimidyl)-4-methyl-, (4-pyridyl)-, and S-(Z-furyl)-3-pyrazolidone. Also listed are S-carboxyl-B-oxo-l-phenylpyrazolidine and ethyl 5-carboxyl-3-oxo-l-(p-tolyl)-pyrazolidate.

However, the prior art believed that the 3- pyrazolidone compounds were not useful as primary or chief developing agents in a developer solution, but were only useful in small amounts to assist in activating a material considered a true primary developing agent, such as hydroquinone. A statement of this conception of the capabilities of Phenidone (the most commercially available 3-pyrazolidone at present and used hereinafter to illustrate the operation of the present invention) is found in The Focal Encyclopedia of Photography, 1969 (mentioned here as a substitute for metol as an activator):

As an alternative to metol, phenidone is used in a number of developers. Generally very much smaller quantities of phenidone are needed (around one-tenth of the metol concentration). The resulting developer has characteristics similar to a metol-hydroquinone formula The phenidone-hydroquinone ratio is normally around 1:25 to 1:40 (Desk Edition, P. 409) A typical ratio of Phenidone to such another developing agent is that of llford Developer 1D-68, wherein hydroquinone is the primary developing agent and the quantities are Phenidone 0.13 and hydroquinone 5.0 parts per thousand, representing a 138.5 proportion. Other formulas vary, but in all cases Phenidone is used in relatively small quantities as compared to the present invention, and is merely used to help activate a primary developing agent, which is usually hydroquinone but which may be glycin, chlorquinol, ascorbic acid or some other developing agent.

Representative of prior art showing such a use of Phenidone is British Patent 871,684. Experiment 4 of this patent discloses a composition where a relatively low Phenidone/hydroquinone ratio is used. There is no teaching in this British Patent to use higher Phenidone proportions, nor any suggestion of the greatly elevated primary/secondary developer weight ratio of the present invention. In addition, this patent at best teaches the use of total developing agent percentages over two times as great as those in the present invention.

Further, in U.S. Pat. No. 3,088,824 (Jacobs) there is disclosed a rapid developing solution based upon the use of a decomposable alkali where (see the Examples at Column 5) in one instance one can calculate a Phenidone/chlorhydroquinone ratio of 3621 if the range extremes provided are taken. There is no suggestion in Jacobs of using the higher Phenidone proportions of the present invention, nor of the very low total developing agent percentages of the present invention, i.e., Jacobs requires a minimum of about four times the developing agents of the present invention and, at weight ratios closest those of the present invention, almost ten-fold the developing agent percentages of the present invention.

In summary, neither of the above representative prior art patents suggest the elevated 3- pyrazolidone/secondary developing agent ratios in combination with the lowered total developing agent percentages of this invention will yield an unexpectedly superior developing solution for high contrast, thin emulsion black and white films.

SUMMARY OF THE INVENTION In contradistinction to the prior art, the present invention provides a unique usage for 3-pyrazolidones; that is, the present invention utilizes a 3-pyrazolidone as a primary developing agent. So as to avoid confusion due to repetition, hereafter the present invention will be discussed primarily in terms of Phenidone as the 3- pyrazolidone, It shall be understood that this is merely for purposes of illustration and not as limitative of the invention.

By the term primary developing agent" is meant that the Phenidone is present in an amount which causes it to be responsible for more of the development than is any other developing agent or developing agents present. This is shown in Table I, wherein examples A and A produce less density than A, which is a combination of developing agents in accordance with the developer of the present invention. This is to say, Phenidone is essential in the developer of the present invention and may not be substituted for or omitted (except, of course, with another developer of the 3- pyrazolidone group or a mixture of 3pyrazolidones); other agents used in conjunction with the Phenidone may be replaced (as explained hereinafter) without destroying the effectiveness of the developer of the present invention. Quantitatively, primary" means that the 3-pyrazolidone is present in an amount greater by weight than the secondary developing agent or the sum of secondary developing agents also present.

The 3-pyrazolidone and secondary developing agent (in the present invention the use of these terms in the singular is for purposes of simplicity; mixtures of 3- pyrazolidones and secondary developing agents are contemplated) are present at a high 3-pyrazolidone ratio and at a low absolute developing agent percentage. The simultaneous use of elevated relative 3- pyrazolidone proportions and lowered absolute developing agent amounts is the essential concept of the present invention. The 3-pyrazolidone in the end use developer is present in an amount of from about 0.000246 to about 0.0128 moles/liter, and 3- pyrazolidone: secondary developing agents are present at a molar ratio of at least about 2.72:1 up to about 13.511.

In addition to correcting the prior art by providing a usable developer wherein Phenidone is the primary developing agent, the present invention further provides a developing process which enables high contrast film to render normal gradation of tones and a process for making a developer concentrate. Normal gradation is another way of saying long-tone-scale; both refer to negatives which distinguish a large number of tones in an image, which is not possible when a film is developed to a high contrast (high gamma or Contrast index), when only a few tones can be visually distinguished.

In its broadest terms, the present invention thus provides firstly a developer comprising an aqueous alkaline solution of a 3-pyrazolidone such as 1-phenyl-3- pyrazolidone (Phenidone) as a primary developing agent and another developing agent which in combination with the B-pyrazolidone yields a super-additive developer solution. Super-additivity is described by TH. James in The Journal of Photogrpahic Science (Vol. 2, 1954): The combination of two developing agents sometimes shows greater photographic activity than would be expected from the activities of the separate developing agents (p. 172).

The invention further provides a process for developing high contrast thin emulsion black and white films to produce continuous tones which essentially comprises applying the above developing solution to a high contrast negative emulsion.

Thirdly, the invention provides a highly concentrated form precursor of the developer solution and a process for forming the same.

It is thus an object of the present invention to provide a developer solution, a developer concentrate from which the developer solution is prepared, a process for preparing the developer concentrate and a development process for thin emulsion, high contrast films which produces continuous print tones, enables said high contrast films to be enlarged to produce fully detailed photographs with magnificent retention of clear detail, and enables said films to be utilized at shorter exposures than with other developers, e.g., three to four stops faster.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a developer solution and a process utilizing the developer solution which enables high contrast, thin emulsion films to be developed so as to yield a continuous-tone image at an Exposure Index which is comparable to the continuous-tone images obtainable using negative materials with thicker emulsions and high silver halide granularity.

As heretofore indicated, the term high contrast very thin emulsion film refers to films such as Kodak High Contrast Copy Film and Fuji Microfilm Negative HR. Other films illustrating characteristics of these two exemplary films could be utilized. The primary characteristic of thin emulsion films is, as compared to most conventional films, is that they contain an equivalent amount of silver salt but lowered gelatin content, thereby having a thinner coated layer. The new thinemulsion films have an emulsion layer of approximately twenty five microns, on a filmbase of about 100 microns, while the older films had emulsion layers of forty to 80 microns, on the same thickness of filmbase. However, they both have about the same amount of lightsensitive silver halide. See, e.g., Photographic Chemistry, by John & Field, Reinhold Publ. 1963; p. 30-33. By the utilization of the developer solution prepared from the developer concentrate and the process of the present invention, such films can be exposed so as to produce continuous-tone negatives at an Exposure Index of approximately 25. This is far superior to any Exposure Index obtained with other processes for such an application of these films.

By the term high contrast" is meant, in the context of the present application, those films which according to the film manufacturer's recommended processing produce a gamma of 1.5 or more and which have hitherto not produced a gamma of 1.0 or lower, withsaid processing. The developer and processing of the present invention enable one to obtain, e.g., gammas of 0.5 to 1.2, preferably 0.5 to 0.9.

Numerical expressions for the measurement of Contrast have been developed, the older one, Gamma, being based upon a graphical measurement of the slope of the straight line portion of the characteristic curve (H&D curve) prepared from density measurements made on a photographic image. However, in more recent years, this has not been as useful as a measurement taking into account the curved lower (toe) and upper (shoulder) portions of the curve, and a method for this has been published by Niederpruem, Nelson & Yule in Phot. Sci. & Eng. vol 10, No. 1, January/February 1966, pages 35-41, and they term their measurement Contrast Index to distinguish it from the older Gamma. See also the article by Edward Scully, Camera 35, pages 44-65, Oct/Nov 1965 issue. The two terms are related, since they are measurements taken from the same Characteristic Curve, but the newer, Contrast Index, uses a longer portion of the curve than the former. In many cases the numerical result is almost identical; in some types of film, the Contrast Index will be somewhat higher; for example the gamma would be 1.5, and the Contrast Index, 2.0 from the same curve, as in these thin emulsion, normally high-contrast films. The term high contrast can thus also be used to delineate those films which, under current processing, illustrate a Contrast Index of not less than about 2.0, and which heretofore have been undevelopable to a Contrast Index of 1.0 or lower when exposed at a generally practical Exposure Index of 25. Using the developer of the present invention and following the processing teaching, it is feasible to obtain Contrast Indexes lower than one-half of those obtainable utilizing developers of the prior art and the processes of the prior art.

By the use of the developer solution of the present invention and following the process teaching, it is entirely feasible to obtain gamma values lower than onehalf of those obtainable utilizing the manufacturers recommended processing.

One of the most unique aspects of the present invention is that the developer solution and process of the present invention make use of a 3-pyrazolidone, such as Phenidone, as the primary developing agent in very low absolute amounts. It is this fact which enables the unique and desirable advantages heretofore set forth to be obtained. As indicated, Phenidone has been used in the prior art in very small quantities to obtain a superadditive effect with another primary developer. The present invention is based upon the discovery that 3- pyrazolidones such as Phenidone serve as a primary developer for high contrast, thin emulsion films when used at a high 3-pyrazolidone ratio and at a low absolute amount of developing agents.

In the developer of the present invention as it is utilized, there is present from about 0.0096 gram to about 0.50 gram of Phenidone in 240 ml of aqueous alkaline solution. When other 3-pyrazolidones are used, they are substituted on a mole for mole basis for Phenidone, e.g., somewhat greater weights of a higher molecular 3-pyrazolidone would be needed.

We have found that Phenidone, when utilized in combination with an activator or secondary developer, in minor proportions within the range stated previously, yields a developer which shows a superadditive effect. This is not the superadditive effect of the prior art wherein other primary developing agents were activated" with Phenidone. On the contrary, our unique system is found when Phenidone itself is used and activated as a primary developing agent.

Representative secondary developing agents or activators for Phenidone are chlorohydroquinone, photographic glycin, orthophenylenediamine and ascorbic acid.

All of the secondary developing agents usable in the present invention are photographic developing agents as specified in the Kendall Rule as modified by Pelz. A discussion of this is given by Tadaaki Tani in the September/October 1971 issue of Photographic Science and Engineering, Pages 374383, hereby incorporated by reference. in summary form, according to Kendalls Rule substances are developing agents if they have the following structure:

a c=c} a where a and a are OH, NH,, NHR,

NR,R and m or a whole number. According to Pelzs rule, substances which have the fol lowing structure are also developers:

aigcsg a Additional material relating to these rules may be found at: J. D. Kendall, lX Congres Intern. de Photographic Scientifique et Appliquee, Paris, 1935, LP. Clere, ed., Editions Rev. dOptique, Paris, 1936, p. 277. W. Pelz, Angew, Chem., 66: 231 (1954).

These secondary developing agents are used at a mole for mole substitution for hydroquinone.

An inexpensive and readily available material usable as an activator for Phenidone is hydroquinone. We are not exactly sure why the hydroquinone serves to activate the Phenidone which is the primary developing agent in the developer of the present invention, but such has been observed time and time again in experimentation. In fact, if hydroquinone is present in major proportions, i.e., Phenidone is not the primary developing agent, it has been found that the developing solution is inoperable as a continuous-tone developer for high contrast films. The fact that a solution using hydroquinone in small quantities and Phenidone as the primary developing agent is a satisfactory developer for continuous-tone processing of high contrast films is unsuspected by the prior art.

ln the developer of the present invention as it is utilized, the Phenidone primary developing agent and the secondary developing agent, e.g., hydroquinone, are present at a ratio within the range of 20:1 to 4.011 by weight as are all proportions specified herein unless otherwise indicated. This weight ratio converts to a molar ratio of l3.5:l to 2.72:1 for the 3-pyrazolidone: secondary developing agents in general.

To illustrate the super-additive or synergistic effect of Phenidone and hydroquinone used within the range of ratios specified above, we compounded three developer concentrates from the ingredients of Example A (see below), one including only 0.16 grams hydroquinone as developing agent, a second including only the 1.1 grams of Phenidone, and a third complete as specifled. We then exposed three pieces of Kodak High Contrast Copy film under identical conditions and, diluting 6 ml of the concentrates with water to make 8 oz. of working developing solution, developed the pieces of exposed film, one in each of the above compounds, at

68F for 12 minutes. Densities above film base of .04

were as follows:

TABLE 1 Example A with hydroquinone only -.00

Example A, with Phenidone only .56

Example A, with both Phenidone and hydroquinone in the present invention a photographic preservative (antioxidant) for the Phenidone is used in an effective amount. The most preferred preservative is sodium sulfite. However, any preservative can be employed. Usually an amount less than the solubility limit will be used to avoid solids precipitation in the liquid. The minimum amount of preservative is not overly critical, and can easily be determined by one skilled in the art since the preservative of the present invention accomplishes its primary art-recognized antioxidant function. The solutions may contain one or more preservatives such as an alkali sulfite, for example, sodium or potassium sulfite, an alkali bisulfite, such as sodium or potassium bisulfite, or an alkali metabisulfite, such as sodium or potassium metabisulfite. One advantage coincidental with the use of an alkali sulfite as the preservative is that it is a mild alkali as well and helps to buffer the pH of the developer concentrate and the diluted developer solution.

The most successful formulations of the developer of the present invention have been in the pH range of 8 to 12, preferably 9.0 to l 1.0. However, the concept of the 3-pyrazolidone primary developing agent is appli cable to the entire range of alkalinity, pH 7.0 to 14. The most preferred developer compositions have been within the narrower pH range because the energy of the Phenidone is diminished as the pH of the developer solution approaches neutrality, and at higher pHs (over pH 11.0) the Phenidone becomes a less selective developer; that is, it tends to reduce to metallic silver even those grains of silver halide which were not exposed to light and therefore which were not a part of the latent image. This latter condition is known as chemical fog, and its effects can be reduced or eliminated, if it is desirable to utilize the concepts of the present invention at a high degree of pH, by addition of an antifoggant to the developer solution. Such an anti-foggant is benzotriazole, but it could be any of the anti-foggants known to the art,

Since the compositions of the present invention are used in the alkaline pH range, it is necessary to add alkaline material to insure an alkaline pH. As indicated, at lower alkaline pH s the preservative, e.g., sodium sulfite, is sufficiently alkaline for this purpose. However, often an additional alkali is needed to arrive at a preferred pH level. For instance, sodium carbonate can be used in conjunction with the mild alkalinity of the sodium sulfite preservative to arrive at the preferred levei of pH. However, any alkali as is used in the photographic arts can be used in the developer concentrate (and, of course, the developer solution); for instance, in addition to the developing agents and preservative, the preferred developer solutions will usually contain an alkali such as sodium carbonate, potassium carbonate, trisodium phosphate, sodium pyroborate, sodium metaborate, sodium hydroxide, potassium hydroxide, etc.

It is to be understood that the foregoing discussion of pH ranges applies to a given developing time and temperature, in this case 68F and 12 minutes. An increase or decrease of the pH level could be compensated for by a manipulation of the time and/or temperature. For instance, an increase in the alkalinity of the developing solution from, say, a pH of 9.7 to 10.7, might require a reduction of developing time from 12 minutes to 9 minutes to prevent an undesirable increase in highlight density and an inordinate amount of fog.

The amount of Phenidone in the developer solution which is used has heretofore been described as being from about 0.0096 to about 0.50 gram in 240 ml of aqueous alkaline solution at a pH of 8.0 to 12.0. While developing can be conducted outside this range, we have found that this range forms the optimum range for the present invention and that if one strays outside this range (for the developing parameters recited hereinafter) one obtains inferior results. For instance, as one approaches 0.50 gram of Phenidone per 240 ml of developer solution, the end print becomes subject to blotching, a serious fault. Further, as Phenidone approaches 0.0096 gram per 240 ml of developer solution, the end print is subject to blocking, another serious fault. Needless to say, these factors are variable, for instance, if one is willing to use a very dilute concentration for an extremely lengthy period of time, a product will result. Alternatively, one may utilize a very concentrated solution for a lesser period of time and obtain a product. However, one must observe the preferred concentrations to realize the full advantages and quality of the present invention.

We have found that there is a very important interrelationship between the Phenidone primary developing agent and the other constituents of the developer solution. For instance, when one uses amounts of Phenidone approaching 0.0096 gram per 240 ml of developer, greater amounts of hydroquinone proportionately are required, e.g., approaching 0.0024 grams and- /or a more alkaline condition is required, e.g., approaching 12. On the other hand, when one uses about 0.50 gram of Phenidone per 240 ml of developer, lower proportionate amounts of hydroquinone (say 0.025 grams) are required. At the lower ratio of hydroquinone to Phenidone of :1 there is a greater concentration of developing agents per 240 ml of the developer solution and the developing time will be shorter time for the higher ratio of hydroquinone to Phenidone of 4:1 which is a relatively weaker developer solution requiring a longer developing time.

This same general trend is, of course, illustrated for the other 3-pyrazolidone/secondary developing agent combinations heretofore mentioned.

If one is to realize the maximum advantages of the present invention, one must observe the aforementioned limits. The present invention provides limits which enable one to obtain a photographic negative from a high contrast, thin emulsion film which is truly astounding and encounters none of the faults of the approximations of the prior art.

It is to be understood, with regard to the alkalinity of the developer solution in general, that higher alkalinity increases contrast, fog, and graininess, as lower alkalinity decreases or minimzes them. Since the contrast through lenses, enlarging illumination systems, and workers preferences as to tonality and other aspects of the final photograph vary, and since, as is obvious, the effects of all variables can be additive, individual preferences within the ranges specified herein can differ appreciably.

One problem often encountered with the use of Phenidone as a substantial ingredient is that Phenidone is difficult to dissolve in water. Phenidone more easily dissolves in an alkaline solution, hence the requisite of an aqueous alkaline solution for the compounding. As will be seen shortly, this plays an important part in the compounding of the developer of the present invention as a developer concentrate.

So far we have offered a fairly generalized discussion of the developer, developer concentrate, developer solution, and developing process of the present invention. However, allof the above materials are useful in the practice of the present invention, though we have found that certain very special formulations offer the best results. The following examples indicate two of the most preferred compositions of the present invention. All parts, except water, are in grams:

The following examples illustrate additional embodiments of the invention:

Example C (Concentrate) Sodium Sulfite 16.00 Phenidone .80 Sodium Carbonate 1.20 Paraformaldehyde .075 I-Iydroquinone .15 Water to make 132 ml For working solution add water to make 2.1 liters *polymeric material In Example C, paraformaldehyde combines with the sodium sulfite to yield sodium hydroxide, a fixed alkali, i.e., an unbuffered alkali.

These compositions were formulated as follows: In Example A (a developer concentrate) two separate solutions were prepared. In the first, a small quantity of water, about 2 ounces. To this was added to 0.16 gram hydroquinone, and when the hydroquinone was dissolved, the 4.6 grams of sodium carbonate were added, to make the aqueous alkaline solution necessary for the dissolution of the Phenidone. To this solution, then, was added the 1.1 grams of Phenidone, which dissolved in 5 to 10 minutes at a temperature of approximately 130F.. In a second and separate mixing container, a solution of the remainder of the sodium sulfite was made with another quantity of water, about 2 ounces. When both solutions were clear, the constituents being completely in dissolution, the first was added to the second and the resulting single solution brought to a volume of 132 ml. For use, water was added to 6 ml of the developer concentrate to make 8 ounces of developer solution, which was then utilized at a temperature of 68F. for 12 minutes. Example C was similarly formed.

In Example B, as in Example A, a two-solution mixing procedure was followed. In the first, 1 gram of the sulfite was added to about 1 ounce of water and then the sodium carbonate was added. To the resulting solution the Phenidone was added, and at a temperature of approximately 180F. dissolution was complete in about minutes. A second solution was prepared embodying the remainder of the sulfite and the 0.10 grams of hydroquinone in about 12 ounces of water. When the components of both solutions were completely dissolved, the first solution was added to the second, and for best results, in order to prevent the precipitation of the Phenidone, the temperature of the second solution was 130F. Subsequently, the volume of the resulting single solution was brought to 16 ounces, and it was stable at room temperature. For use, water was added to one-half ounce of the stock solution to make 8 ounces of developer solution, and development took place satisfactorily at a temperature of 68F. in 16 to 20 min utes.

In Example C, two separate solutions are prepared. in the first, a small quantity of the sodium sulfite, about 1 part, is dissolved in a small quantity of water, about 1 ounce. To this is added the 0.075 parts paraformaldehyde and 1.20 parts sodium carbonate to yield an aqueous alkaline concentrate. To this is added the 0.80 parts Phenidone, which dissolves readily at a temperature of about 90F. In a second and separate mixing container a solution of the remainder of the sodium sulfite and the 0.15 parts of hydroquinone is made with about 3 ounces of water. When both solutions are clear, the constituents being completely in dissolution, the first is added to the second and the resulting single solution brought to a volume of 132 ml. For use, water is added to 6 ml of the developer concentrate to make 8 ounces of developer solution, which is then utilized at a temperature of 68F. to about 72F. for 16 minutes.

Sodium sulfite is common to all examples. This is the most preferred preservative of the present invention, and accordingly was the one utilized in the examples. in all examples, Phenidone is the primary developing agent, present in amounts much greater than that of hydroquinone. As will be appreciated, the final volume of solution for the developer concentrate or stock solution can be varied. The volume given here are those with which we obtained entirely satisfactory results.

It is important when forming a developer concentrate to make sure that the alkaline components of the developer are used to their greatest advantage to aid in the dissolution of the Phenidone. That is why in all examples very small quantities of water were used initially in the preparation of the solution into which the Phenidone was dissolved.

The developer concentrate can thus be seen to directly yield the end use developer of the present invention merely upon dilution, usually a 10 to 40-fold volume dilution with water. Generally, the absolute amounts of the components in the concentrate will thus be, for 1,000 ml of concentrate, from about 2.5 to about 10.0 grams Phenidone, hydroquinone within the ratios heretofore recited and sufficient preservative to prevent oxidation, all at a pH of about 10.0 to about 10.5. Of course, on a mole for mole substitution the other 3-pyrazolidones and secondary developing agents may be used within these ranges.

All examples exhibit the use of a buffered alkali, and the pH of the developer solution in both instances is in the narrow preferred range of 9.0 to 11.0.

Additional deveioper formulations were also prepared and tested. These are described below.

The basic formula tested was prepared as follows:

40 ml water at 140F.

l g anh. sodium suifite 0.16 g hydroquinone 4.6 g sodium carbonate monohydrate 1.1 g l-phenyl3-pyrazolidone water to make 120 ml 8 g anh. sodium sulfite water to make 132 ml at 68F.

The chemicals were added in the order shown. Each chemical was completely dissolved before the next added. This formula was modified by substituting the various developing agents of interest for hydroquinone on a mole for mole basis The developing agents used in this study were:

City Chemical Phenidone (Phenidone A") l-phenyl-3-pyrazolidone Kodak Hydroquinone 1,4-dihydroxybenzene Edwal Monazol (Glycin) (p-hydroxyphenylamino)-acetic acid Edwal Orthamine p-phenylenediamine dihydrochloride Kodak Ascorbic Acid Mallinckrodt Pyrogallol 1,2,3-tr1'hydroxybenzene Kodak Chlorohydroquinone 2-chloro-1,4-dihydroxybenzene The amounts of materials tested are shown below.

L-(+)-ascorbic acid The tests were performed as follows. The exposures were made on a Kodak Model 101 Process Control Sensitometer containing a General Electric A.S.A. type BMY lamp operated at a color temperature of 2,8501( to provide an illuminance of 1,700 meter-candles incident at the film plane. This radiation was attenuated by a 1.4 neutral density filter, a Kodak No. 2 step tablet and two plastic pieces mounting the step tablet to provide a proper scale of exposures for the film used (35 mm H & W film 040 0251 1 14). The exposure time was one-fifth second. The exposure levels on the film passing through alternate steps are shown in Steps 17, 11 and 3 of the Kodak No. 2 step tablet used (B).

The film was processed at 68F (water-bath thermostated) for 14 minutes. It was held in the outer turn of the bottom reel, emulsion inward, in a two-reel Nikor tank. The agitation was constant, gentle agitation for the first 2 minutes" (one inversion and righting of the tank each 2 seconds) and three turns at the beginning of each minute thereafter. The Nikor tank was in the thermostat whenever the agitation was not being performed. Film pieces between 6 and 7 inches in length were processed, no more than one piece of film at a time.

The various formulas were prepared as concentrates and diluted for processing 10% milliliters of concentrate brought up to 8 fluid ounces with distilled water at 68F.

This processing, each time checked, gave acceptably reproducible results for the formulations reported here.

Densities were read on a MacBeth Model "I'D-2 Transmission Densitometer using a 2 mm aperture.

The results are shown below.

TABLE OF RESULTS Number Basic Formula Variation Density at Steps 17 11 3 phenidone only 0.18 0.56 0.80 hydroquinone only 0.04 0.04 0.04 phenidone &. hydroquinone 0.28 0.88 1.22 phenidone only 0.18 0.56 0.80 glycin only 0.04 0.04 0.06 phenidonc & glycin 0.18 0.68 0.97 phenidone only 0.18 0.56 0.80 orthamine only 0.04 0.04 0.04 phenidone & orthamine 0.17 0.73 1.04 phenidone only 0.18 0.56 0.80 ascorbic acid only 0.04 0.04 0.04 phenidone & ascorbic acid 0.18 0.68 0.92 phenidone only 0.18 0.56 0.80 pyrogallol only 0.04 0.04 0.04 phenidone & pyrogallol 0.18 0.61 0.86 phenidone only 0.18 0.56 0.80 chlorohydroquinone only 0.04 0.04 0.04 phenidone & chlorohydroquinone 0.18 0.70 0.96

*Cleared base plus fog equals a density of 0.04.

It will be appreciated that the Table of Results above shows only uses in a molar amount equivalent to hydroquinone, which is the most preferred secondary developing agent within the present invention. It will further be apparent to those skilled in the art that within the class of super-additive secondary developing agents encompassed by the above formulae certain agents offer preferred results, i.e., those enumerated above.

The following offers to one skilled in the art instructions in the use of the preferred forms of the present invention. It is offered to further explain the developing process. To practice the process, the developer solution shown in Example A was used.

In the present instance, Kodak High Contrast Copy Film (Improved Type 5069) was exposed out-of-doors at an Exposure Index of 25, with the individual exposure for each frame being determined by the Kodak Daylight Exposure Dial, an incident light measurement with a Gossen Luna-Pro, and a reflected light measurement with a Minolta Auto-Spot 1 meter.

Using the above working developer solution, the development was at 68F for 12 minutes. During the first 2 minutes of development the developing tank was given constant gentle agitation (one inversion and righting of the tank each 2 seconds) to ensure the uniform and complete contact of the developer solution with the negative emulsion. During the remainder of the development time the developing tank received 6 seconds of agitation each minute to ensure a supply of fresh developer evenly throughout the tank and in contact with the negative emulsion. At the completion of the development time, 12 minutes in all, the film was removed and the processing was completed in a conventional manner. An acidic stop bath or a plain water rinse follows the developer. The fixing time is shorter than for other films, with about 2 minutes being sufficient. A hypo clearing bath or plain water can be used. Subsequent handling and storage are normal.

The preferred conditions are development for about 2 minutes to about 128 minutes at about 65F. to about 80F with most developments being conducted in from about to about minutes. This last time range will generally sufi'ice for most users.

As indicated above, certain conditions must be maintained in the development process. Just as the timetemperature inter-relationship can be varied for a given concentration of the developer solution, so, too, can the concentration be varied as a further function of the processing interrelationships. In the cases of the developers described above, however, best results were obtained by adhering to the conditions specified.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. An aqueous developer solution for developing high contrast, thin emulsion light sensitive silver halide films to a gamma in the range of from about 0.5 to about 1.2 which comprises an aqueous alkaline solution, in the pH range of 8 to 12, of: A

a 3-pyrazolidone as the primary developing agent,

at least one secondary developing agent which in combination with the 3-pyrazolidone yields a super-additive developer and an antioxidant preservative, the 3-pyrazolidone being present in an amount of from about 0.000246 to about 00128 moles per liter, and the molar ratio of the 3-pyrazolidone to secondary developing agent being at least about 2.72:1.

2. The developer solution of claim 1, wherein the at least one secondary developing agent is selected from the group consisting of hydroquinone, glycin, orthamine, chloroquinone, ascorbic acid, pyrogallol or mixtures thereof.

3. The developer solution of claim 1, wherein the secondary developing agent is hydroquinone.

4. The developer solution of claim 3, wherein from about 0.000246 to about 0.0128 moles of l-methyl-3- pyrazolidone is present per liter of developer solution. 5. The developer solution of claim 4, wherein the molar ratio of the 3-pyrazolidone primary developing agent to the at least one secondary developing agent is from about 2.72:1 to about 13.521.

6. A process for producing negatives with a gamma of about 0.5 to about 1.2 on exposed high contrast, thin emulsion light sensitive silver halide films which comprises:

applying to said film the developer solution of claim 1 for a period of time and a temperature sufficient to reduce the exposed silver halide in the film,

removing said film from the developer solution after said time and thereafter conventionally treating said film so as to remove from the emulsion residual unexposed and undeveloped silver halide.

7. The process of claim 6, wherein the time is from about 2 to about 128 minutes.

8. The process of claim 6, wherein the temperature is from about 65F to about F.

9. The process of claim 8, wherein the time is from about 10 to about 20 minutes.

10. A concentrate of the developer solution of claim 1, comprising the 3-pyrazolidone primary developing agent, and the at least one secondary developing agent and the antioxidant preservative, the concentrate being at a pH greater than the pH of the developer solution and containing a greatly reduced amount of water, which concentrate upon dilution with water yields the developer solution of claim 1 at a pH of from about 8 to about 12.

11. The concentrate of claim 10, wherein the dilution with water is at least 10 fold, by volume.

12. A process for forming the concentrate of claim 10 comprising the sequential steps of:

forming an aqueous alkaline solution at an elevated pH containing the secondary developing agent in tion the predetermined amount of the 3- pyrazolidone, addition being at an elevated temperature.

- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,772, 019 Dated November 13, 1973 Inventor(s) HAROLD HOLDEN ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Colunm 10, line 44, which presently reads lutions were prepared.

In the first, a small quantity of" should be amended to --lutions were prepared. In the first, 1 gram of sulflte was added to a small quantity of--.

Column 12, line 19, delete "p-phenylenediamine", insert --o-phenylenedlamine--.

Column 14, line 30 (claim 4, line 2), delete "methyl" insert --phenyl--.

Signed and sealed this 17th day of September 1974.

(SEAL) I Attest: I

McCOY M. GIBSON JR. Attesting Officer C. MARSHALL DANN Commissioner of Patents ORM powso USCOMM-DC 60376-P69 fi' LLS. GOVERNMENT PRINTING OFFICE: I969 O-"SEG-SSL 

2. The developer solution of claim 1, wherein the at least one secondary developing agent is selected from the group consisting of hydroquinone, glycin, orthamine, chloroquinone, ascorbic acid, pyrogallol or mixtures thereof.
 3. The developer solution of claim 1, wherein the secondary developing agent is hydroquinone.
 4. The developer solution of claim 3, wherein from about 0.000246 to about 0.0128 moles of 1-methyl-3-pyrazolidone is present per liter of developer solution.
 5. The developer solution of claim 4, wherein the molar ratio of the 3-pyrazolidone primary developing agent to the at least one secondary developing agent is from about 2.72:1 to about 13.5:1.
 6. A process for producing negatives with a gamma of about 0.5 to about 1.2 on exposed high contrast, thin emulsion light sensitive silver halide films which comprises: applying to said film the developer solution of claim 1 for a period of time and a temperature sufficient to reduce the exposed silver halide in the film, removing said film from the developer solution after said time and thereafter conventionally treating said film so as to remove from the emulsion residual unexposed and undeveloped silver halide.
 7. The process of claim 6, wherein the time is from about 2 to about 128 minutes.
 8. The process of claim 6, wherein the temperature is from about 65*F to about 80*F.
 9. The process of claim 8, wherein the time is from about 10 to about 20 minutes.
 10. A concentrate of the developer solution of claim 1, comprising the 3-pyrazolidone primary developing agent, and the at least one secondary developing agent and the antioxidant preservative, the concentrate being at a pH greater than the pH of the developer solution and containing a greatly reduced amount of water, which concentrate upon dilution with water yields the developer solution of claim 1 at a pH of from about 8 to about
 12. 11. The concentrate of claim 10, wherein the dilution with water is at least 10 fold, by volume.
 12. A process for forming the concentrate of claim 10 comprising the sequential steps of: forming an aqueous alkaline solution at an elevated pH containing the secondary developing agent in substantially the minimum amount of water necessary to dissolve the secondary developing agent and a predetermined amount of a 3-pyrazolidone, and adding to and dissolving in the aqueous alkaline solution the predetermined amount of the 3-pyrazolidone, addition being at an elevated temperature. 